Journal of Geophysical Research: Space Physics最新文献

{"title":"A Time-Dependent Model of the Vibrational Distribution of Nitrogen Molecules: New Rate Data Sets and Self-Consistent Coupling With Auroral and Ionospheric Electrons","authors":"Jun Liang,&nbsp;J.-P. St-Maurice,&nbsp;E. Donovan","doi":"10.1029/2025JA034301","DOIUrl":"10.1029/2025JA034301","url":null,"abstract":"<p>Vibrationally excited nitrogen molecules (N₂) play an important role in the chemistry and dynamics of Earth's atmosphere. Electron impact, whether it originates from auroral precipitation or ionospheric thermal electrons, is among the major causes of the vibrational excitation of N₂. Due to the co-existence of excitation and deexcitation, the net energy exchange between electrons and N₂ molecules depends on the N₂ vibrational distribution, so that the electron energy distribution and the N₂ vibrational distribution are inherently coupled. In this study, we introduce a new model to simulate the time-dependent vibrational distribution of N₂, incorporating self-consistent ionospheric dynamics and mutual energy exchange with auroral suprathermal electrons and ionospheric thermal electrons. We demonstrate that the model runs under strong auroral precipitation and strong heating conditions within the framework of our previously established Transition Region Explorer Auroral Transport Model (TREx-ATM). We elucidate the time-varying characteristics of the N₂ vibrational state densities, their altitude profiles and major contributing mechanisms, as well as the dynamic coupling among the N₂ vibrational distribution, the auroral suprathermal electrons, and the ionospheric thermal electrons. A few notable effects of the intensified N₂ vibrational excitation on the ionospheric and thermospheric chemistry are addressed. Our model may help advance the understanding of the role and dynamics of vibrationally excited N₂ in cross-regional coupling under disturbed times.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034301","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ULF Wave-Driven Energization of Plasmaspheric Plume Ions During Multi-Step Geomagnetic Storms","authors":"Yingying Zhao,&nbsp;Hui Zhu,&nbsp;Huicong Chen,&nbsp;Zhijie Qin,&nbsp;Zhenghao She","doi":"10.1029/2025JA034430","DOIUrl":"10.1029/2025JA034430","url":null,"abstract":"<p>We report direct observations of the energization of plasmaspheric plume ions by ultralow frequency (ULF) waves during a multi-step geomagnetic storm from 25–29 August 2015. Based on Van Allen Probes observations, we identify multiple plasmaspheric plume regions in the afternoon-dusk sector during the storm, characterized by highly irregular density structures. Concurrently, the cold (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&lt;</mo>\u0000 <mn>100</mn>\u0000 </mrow>\u0000 <annotation> ${&lt; } 100$</annotation>\u0000 </semantics></math> V) ion fluxes exhibit intermittent enhancements within these regions. A detailed analysis reveals that the ion flux variations result from the modulation of the ULF wave-driven <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>E</mi>\u0000 <mo>×</mo>\u0000 <mi>B</mi>\u0000 </mrow>\u0000 <annotation> $Etimes B$</annotation>\u0000 </semantics></math> drift. Interestingly, the modulated ion fluxes appear at near <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>90</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $90{}^{circ}$</annotation>\u0000 </semantics></math> pitch angles and occur only in high-density plumes; no modulation signatures appear in low-density plasma troughs. These observations strongly support that ULF waves can perpendicularly modulate plasmaspheric plume ions within high-density regions via <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>E</mi>\u0000 <mo>×</mo>\u0000 <mi>B</mi>\u0000 </mrow>\u0000 <annotation> $Etimes B$</annotation>\u0000 </semantics></math> effects. The present results provide a deeper understanding of the interactions between ULF waves and plasmaspheric plume ions in the inner magnetosphere.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermospheric Gravity Waves and Ionospheric Disturbances Triggered by Mountain Waves Over the Western US in January 2017","authors":"Erich Becker,&nbsp;Sebastijan Mrak,&nbsp;Sharon L. Vadas,&nbsp;J. D. Huba","doi":"10.1029/2025JA033951","DOIUrl":"10.1029/2025JA033951","url":null,"abstract":"<p>We analyze an episode of strong mountain wave (MW) activity over the western US from 9 to 12 January 2017 using the HIgh Altitude mechanistic General Circulation Model. We find that medium-scale MWs were generated by strong eastward flow over the Sierra Nevada and the Rocky Mountains. During this time, part of the stratospheric polar vortex jet extended from the western US to eastern Canada such that the MWs propagated into the lower mesosphere where they dissipated from westward vertical wind shear. This resulted in secondary gravity waves (GWs) that propagated into the lower thermosphere where tertiary GWs having concentric ring structures were created. With increasing altitude in the thermosphere, certain propagation directions were highlighted as a result of the dissipation induced by the tidal winds. At 260 km, we find eastward propagation during local morning over the northeastern US, equatorward propagation around local noon over the southern US, westward propagation during local afternoon over the northwestern US, and poleward propagation over Canada after local midnight. In addition, the model shows equatorward propagating larger-scale GWs over Canada from remote sources around local noon. The simulated regional GW-mean flow interaction patterns are consistent with multi-step vertical coupling triggered by the MWs. The traveling ionospheric disturbances (TIDs) during the MW event are simulated with the ionospheric model SAMI3. The simulated GWs and TIDs are consistent with the medium-to-large-scale TIDs observed over the continental US in GPS TEC data.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic Rayleigh-Taylor Instability in Solar Atmosphere Downward Magnetic Flux Transport","authors":"W. Harhad,&nbsp;A. Bouabdallah,&nbsp;T. H. Abdelatif,&nbsp;S. NaitAmor,&nbsp;Z. Meliani","doi":"10.1029/2025JA034214","DOIUrl":"10.1029/2025JA034214","url":null,"abstract":"&lt;p&gt;Descending cold plasma structures are observed and are thought to result from the Magnetic Rayleigh&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;-&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mbox{-}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;Taylor Instability (MRTI), which facilitates the downward transport of plasma toward the photosphere and contributes to the restructuring of the magnetic field. In this study, we perform 2.5D nonlinear compressible magnetohydrodynamics (MHD) simulation using the open&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;-&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mbox{-}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;source MPI&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;-&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mbox{-}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;AMRVAC code to investigate the role of MRTI under chromospheric&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $/$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;photospheric conditions. Our results show that the transverse magnetic field &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;B&lt;/mi&gt;\u0000 &lt;mi&gt;x&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left({B}_{x}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; alters the MRTI growth by modifying the critical wavelength and delaying its onset, while the longitudinal component &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;B&lt;/mi&gt;\u0000 &lt;mi&gt;z&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left({B}_{z}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; governs the buoyancy&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;-&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mbox{-}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;driven dynamics, influencing the size and descent speed of mushroom&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;-&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mbox{-}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;like structures. The height evolution of these structures exhibits a slow linear phase followed by a rapid quadratic phase. Upon reaching the photosphere, their interaction with the surrounding magnetic field further shapes the mushrooms. This study highlights the crucial role of MRTI in the magnetic flux drainage from the chromosphere to the phot","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spontaneous Evolution From Electron-Only to Standard Reconnection in a Force-Free Current Sheet","authors":"Jincai Ren,&nbsp;San Lu,&nbsp;Rony Keppens","doi":"10.1029/2025JA034322","DOIUrl":"10.1029/2025JA034322","url":null,"abstract":"<p>Electron-only reconnection is a novel reconnection regime observed recently in the turbulent magnetosheath and magnetotail, related to energy conversion and large-scale reconnection events. However, the relationship between this novel regime and standard kinetic reconnection is still not fully understood. In this paper, we investigate the spontaneous evolution from electron-only to standard reconnection in a force-free current sheet under guide fields using 2.5-dimensional particle-in-cell (PIC) simulations. Our results reveal that reconnection occurs within the electron-only regime initially, where ion outflow jets and ion heating are absent. This absence is attributed to the spatial limitations of the downstream region, which restricts the influence of electric forces, thereby preventing significant ion acceleration. Consequently, the negligible ion outflow velocities result in minimal work done by the pressure gradient term, and the contribution of ion enthalpy flux remains insignificant, thereby leading to the lack of ion heating during this phase. As reconnection proceeds, the available space for ion acceleration increases, allowing for both ion heating and the development of ion outflow jets, which ultimately results in a temporal evolution to the standard kinetic reconnection regime. We further examine the effect of ion temperature on this temporal evolution and discover that high ion temperature inhibits this temporal evolution from electron-only to standard reconnection, confining reconnection to the electron-only regime throughout the simulation even though the simulation domain is large. This work provides insights into the role of electron-only reconnection in the magnetosheath.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145057898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Testing Field-Line Mapping of Electric Fields in Earth's Magnetosphere","authors":"Yusuke Ebihara,&nbsp;Masafumi Hirahara,&nbsp;Takashi Tanaka","doi":"10.1029/2025JA034108","DOIUrl":"10.1029/2025JA034108","url":null,"abstract":"<p>The convection electric field plays a fundamental role in transporting plasma within the magnetosphere. A widely accepted assumption in both observational and modeling studies is that the electric fields can be instantaneously mapped along magnetic field lines. To evaluate the validity of this assumption, we conducted a global magnetohydrodynamic (MHD) simulation under a southward interplanetary magnetic field, focusing on the electric fields at midnight. Major findings are as follows: (a) The mapping between magnetospheric and ionospheric electric fields is generally imperfect, even when propagation and travel time of Alfvén waves are considered. (b) During the substorm growth phase, ionospheric electric fields are ∼1.5 times larger than those in the magnetosphere. Induction electric fields significantly reduce magnetospheric electric fields. (c) In the substorm expansion phase, the electric fields are highly variable, and the ionospheric electric fields are typically smaller than the magnetospheric electric fields by a factor of ∼6–8. (d) At low <i>L</i>-shells (<i>L</i> = 4–5), magnetic footprints are close to Alfvénic footprints. (e) At high <i>L</i>-shells (<i>L</i> = 6–10), a substantial mismatch exists between magnetic and Alfvénic footprints. The discrepancies between magnetospheric and electric fields are attributed to induction electric fields, external forces acting on plasma, and the insufficient number of interactions between the magnetosphere and the ionosphere. We conclude that field-line mapping of electric fields is marginally valid at low <i>L</i>-shells (<i>L</i> &lt; 5) and under quasi-steady conditions, despite some differences in magnitude. Future studies incorporating dispersive and kinetic Alfvén waves are needed to obtain definitive conclusions.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034108","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Roles of Plasma Sheet Flow, Plasma Sheet Dissipation and the M-I Coupling in Reproducing the Substorm With the Global Simulation","authors":"T. Tanaka,&nbsp;Y. Ebihara,&nbsp;M. Watanabe,&nbsp;S. Fujita,&nbsp;R. Kataoka","doi":"10.1029/2024JA033606","DOIUrl":"10.1029/2024JA033606","url":null,"abstract":"<p>The substorm is reproduced from the REPPU (REProduce Plasma Universe) global simulation. A quasi-steady state is generated under the northward interplanetary magnetic field (IMF), and then the IMF is turned southward to generate the substorm. In the initial state, significant earthward plasma sheet flow is maintained assuming dissipation at the distant tail. Such plasma sheets are not only confined but also convective, where the M-I (magnetosphere-ionosphere) coupling and region-2 field-aligned current (FAC) play a partial role in confinement. Ionospheric convection accelerates the thinning during the growth phase and dissipation in the distant tail makes the near-earth neutral line (NENL) retreat to the mid-tail. 9 min before the onset, the plasmoid, the NENL, and the flux rope are generated from far to near earth. When the dipolarization front (DF) that starts from the mid-tail NENL reaches the near-earth tail, the onset FAC appears through the formation of the near-earth dynamo, followed by the poleward expansion. These processes are projected only to a narrow latitudinal region of the ionosphere. The expansion phase develops appropriately by large dissipation assumed at X points to approximate kinetic effects. Formations of the NENL and the flux rope proceed under a mechanically balanced structure in the plasma sheet, which is realized upon the global conflict among ionospheric convection, magnetospheric flow, magnetic structure and dissipation distribution. Global magnetohydrodynamic (MHD) simulation enables to reproduce such properly balanced structures. Finally, earthward flow from the NENL overwhelms tailward flow from the flux rope, and eventually the whole feature appears the outside-in.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Impact of IMF By Variations on the Evolution of Lobe Reconnection Pattern and the Subsequent Development of the Conjugate Transpolar Arcs","authors":"Yu Wang,&nbsp;Desheng Han,&nbsp;Huixuan Qiu,&nbsp;S. E. Milan","doi":"10.1029/2025JA034262","DOIUrl":"10.1029/2025JA034262","url":null,"abstract":"<p>Under a northward interplanetary magnetic field (IMF) with B_x ∼ 0, conjugate transpolar auroral arcs (TPAs) often appear on opposite polar cap sides in both hemispheres. These TPAs often show movement in response to IMF B_y changes. For example, a negative-to-positive IMF B_y shift moves northern TPAs from dawn to dusk, with southern TPAs moving oppositely. A popular model links these TPAs to lobe reconnection changes, but it's based on single-hemisphere observations and lacks confirming evidence from both hemispheres. In this study, utilizing simultaneous DMSP/SSUSI observations from both hemispheres, we examined a well-chosen event to track the formation and evolution of conjugate TPAs and compared the results with global MHD simulations. We found that: initially, when IMF B_y was ∼ −7 nT, conjugate TPAs were observed in the dawn/dusk side in the Northern/Southern Hemisphere, and MHD simulations showed that single-lobe reconnection occurs at the dawnside/duskside lobe in the Northern/Southern Hemisphere, respectively. As the IMF B_y gradually changed to 0, the TPAs in both hemispheres shifted to the polar cap center and dual-lobe reconnection began to appear in the simulation results. We also notice that there is a transitional phase where both single- and dual-lobe reconnections co-exist before dual-lobe reconnection dominates. Based on these results, we argue that here we provide strong evidence for Milan's model that the evolution of conjugate TPAs is associated with changes in the location and pattern of lobe reconnection driven by variations in IMF B_y.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diffuse Auroral Precipitation Effects on Ionospheric Conductance During Magnetic Storms: Comparison of Simulated and Incoherent Radar Scatter-Inferred Conductance","authors":"Margaret W. Chen,&nbsp;Colby Lemon,&nbsp;James Hecht,&nbsp;George V. Khazanov,&nbsp;J. Scott Evans,&nbsp;Stephen Kaeppler,&nbsp;Christine Gabrielse,&nbsp;Shun-Rong Zhang","doi":"10.1029/2025JA034069","DOIUrl":"10.1029/2025JA034069","url":null,"abstract":"<p>We investigated the effects of storm-time diffuse auroral electron precipitation on ionospheric Pedersen and Hall conductivity and conductance during the CME-driven St. Patrick's Day storms of 2013 (min <i>Dst</i> = −131 nT) and 2015 (min <i>Dst</i> = −233 nT). These storms were simulated using the magnetically and electrically self-consistent RCM-E model with STET modifications, alongside the B3C auroral transport code to compute ionospheric conductivities and height-integrated conductance. The simulation results were validated against conductance inferred from Poker Flat Incoherent Scatter Radar (PFISR) and Millstone Hill Incoherent Scatter Radar (MHISR) measurements. Our simulations show that the magnetic latitude and local time distribution of Pedersen and Hall auroral conductance strongly correlate with diffuse electron precipitation flux, with the plasmapause marking the low-latitude boundary of conductance. Simulated Pedersen/Hall conductance agrees reasonably well with PFISR measurements at 65.9° MLAT during diffuse auroral precipitation. During the intense 2015 storm, diffuse aurora extended down to 52.5° MLAT, with simulated conductance agreeing within a factor of two with MHISR observations. Discrete auroral arcs observed during both storms enhanced PFISR conductance by tens of siemens, though these enhancements were not captured by the model. Additionally, the simulated electric intensity showed development of sub-auroral polarization streams (SAPS) and dawn SAPS features and followed the general trend of Poker Flat electric intensity at 65.9° MLAT during diffuse aurora, despite being updated every 5 min. The overall agreement between simulated ionospheric conductance and electric intensity with observations highlights the model's capability during diffuse auroral precipitation.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034069","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145051234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Observations of Persistent Downstream Magnetic Oscillations at the Earth Bow Shock","authors":"M. Golan,&nbsp;M. Gedalin","doi":"10.1029/2025JA034321","DOIUrl":"10.1029/2025JA034321","url":null,"abstract":"<p>The redistribution of the directed flow energy in a collisionless shock is the central problem of shock physics. The incident ion energy is transferred to ion and electron heating, acceleration of a small fraction of particles, and enhancement of the magnetic field. The mean magnetic field enhancement is determined by the standard boundary conditions. Recently, shocks were observed in which the amplitude of the persisting downstream magnetic fluctuations exceeded the mean downstream field. The question of the ubiquity of the phenomenon is of utmost importance since it would require re-consideration of the boundary conditions. It may also mean that the effective magnetic field in supernova remnant shocks may be currently grossly underestimated. Using the Magnetospheric Multiscale observations of the Earth bow shock, we analyze the dependence of the relative amplitude of the downstream magnetic fluctuations on the main shock parameters. It is found that large fluctuations are typical for quasi-parallel shocks and higher Mach numbers.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034321","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}